The ability to conduct oxide-ions (O2−) allows the use of materials in a variety of applications. For instance, such materials may be used in solid oxide fuel cells, as oxygen sensors, in oxygen separation membranes, in hydrogen production from water, and in any other use where the movement or detection of oxide-ions is desirable.
Many oxide-ion conductive materials have been developed, but they often are too reactive with other components in the systems where they may be used, are not able to tolerate high temperatures, or simply fail to have a high enough oxide-ion conductivity.
For example, one current oxide-ion conductor, which has the general chemical formula La0.8Sr0.2Ga0.83Mg0.17O2.815 has an oxide-ion conductivity (σO) of greater than 10−2 Siemens per centimeter (S/cm) only at temperatures above 600° C. Another oxide-ion conductor, with the general formula Sr0.8K0.2Si0.5Ge0.5O2.9, which is representative of oxide-ion conductors with the general formula Sr1−xAxSi1−yGeyO3−0.5x have an oxide-ion conductivity (σO) of greater than 10−2 S/cm only above temperatures around 625° C. A third type of oxide-ion conductors, with the general formula Sr0.6Na0.4SiO2.8 or the general formula Sr0.55Na0.45SiO2.775, have an oxide-ion conductivity (σO) of greater than 10−2 S/cm above temperatures around 525° C.
Additional super oxide-ion conductors, particularly those with an oxide-ion conductivity (σO) of greater than 10−2 S/cm at lower temperatures are needed.